Why are greenhouse vegetables most prone to calcium deficiency?

Vegetables are calcium-loving crops. When planting, people often pay attention to the application of nitrogen, phosphorus and potassium fertilizers, while neglecting calcium fertilizer. With the large emergence of protected cultivation, it is even more likely to lead to calcium deficiency in greenhouse soil. So, how can crops be supplemented with calcium reasonably?

Choose calcium fertilizer reasonably

Different calcium fertilizers have different properties. The pH of the soil in greenhouses is mostly 6.5-7.5, so alkaline substances or neutral fertilizers should be applied, such as slaked lime, calcium nitrate, etc., while acidic or physiologically acidic substances should be used less. Ordinary phosphate fertilizers such as superphosphate, calcium magnesium phosphate and triple superphosphate are important sources of calcium fertilizer. Bone meal and plant ash both contain a certain amount of calcium and are also calcium sources that cannot be ignored, and can be selected according to the situation.

It is recommended to use water-soluble fertilizers containing calcium and medium and trace nutrient elements (containing not less than 120 g/L calcium, not less than 20 g/L magnesium, not less than 50 g/L zinc, and not less than 3 g/L boron), to supplement other medium and trace elements while supplementing calcium. Pay attention to choosing fertilizers with low salt concentration, which are safer for crops.

Best fertilization period

After vegetables enter the vigorous growth period, soil calcium nutrition begins to decrease, and at the same time the calcium in vegetable leaves begins to decrease. This is the best period for applying calcium fertilizer. In production, to prevent calcium deficiency in the early stage of vegetable growth, calcium fertilizer can be applied as a base application. In greenhouses that have been planted continuously for many years, generally apply 2000-3000 kg of decomposed organic fertilizer per mu, and then add 30-45 kg of superphosphate.

Suitable fertilization method

For vegetable greenhouses with relatively heavy soil acidity, the method of heavy base fertilizer application is mostly used, that is, applying 100 kg of plant ash or 50 kg of slaked lime per mu, so as to regulate the soil pH. The specific method is to mix organic fertilizer with slaked lime or plant ash evenly, apply it evenly on the ground surface, and plow it into the ground.

For growing vegetables, especially after entering the vigorous growth period, the method of topdressing can be used to supplement calcium nutrition. Generally, 40-60 kg of slaked lime is used per mu, and the amount of lime for sandy soil should be appropriately reduced. This can not only supplement calcium, but also help neutralize soil acidity, increase pH, and improve soil aggregate structure. It is also possible to take 80 kg of slaked lime or 50 kg of plant ash, uncover one end of the film, open a furrow 10 cm deep, apply the fertilizer to the bottom of the furrow, then water, and after the water infiltrates, cover with soil and close the film. Or deep plow and adopt plastic film mulching cultivation methods to enhance its water and fertilizer retention capacity, maintain relatively stable soil moisture, and reduce calcium loss. Calcium can also be supplemented by foliar topdressing in combination with disease-prevention spraying. The topdressing concentration is generally 0.3%-0.5%. Generally, 0.1%-0.2% calcium nitrate or 1% superphosphate can be sprayed, once every about 15 days, for 3-4 consecutive sprays, with good results.